Flow rate measuring method and flowmeter, flow rate measuring section package used for them and flow rate measuring unit using them, and piping leakage inspection device using flowmeter

ABSTRACT

Measurements are obtained by a computing unit based on an output Vh from an indirectly-heated constant-temperature controlling flow rate measuring section ( 16 ) and an output Vout from a two-constant-point temperature difference detecting flow rate measuring sections ( 18   a   , 18   b ). In the flow rate measuring section ( 16 ), a heating element ( 163 ) is feedback-controlled based on a detected temperature by a heat sensing element ( 162 ) to obtain an output Vh based on the feedback-controlled condition. An output Vout is obtained from flow rate measuring sections ( 18   a   , 18   b ) based on the detected temperature difference between a heat sensing element ( 182 ) disposed on the liquid-flow-direction upstream side of the flow rate measuring section ( 16 ) and a temperature sensing element disposed on the downstream side. A computing unit outputs as a measurement a flow rate obtained based on the output Vh in a flow rate region where a flow rate is larger than a predetermined boundary flow rate, and outputs as a measurement a flow rate obtained based on the output Vout in a flow rate region where it is less than a boundary flow rate. Accordingly, a flow rate is measured with good precision and sensitivity over a wide flow rate range from a trace-amount flow rate region to a comparatively large flow rate region.

TECHNICAL FIELD

The present invention belongs to a fluid flow rate detection technique,and relates particularly to a method of measuring a flow rate of a fluidflowing through a fluid channel, and a flowmeter for use in the method.The present invention also relates particularly to a flow rate measuringsection package for measuring a flow rate of a fluid flowing through afluid channel, and a flow rate measuring unit using the package.Furthermore, the present invention relates to a device or apparatuswhich inspects a leakage of a liquid from a piping using a flowmeter.The leakage inspection apparatus of the present invention is preferablyused, for example, in inspecting a liquid leakage in a piping whichpumps out the liquid from a fuel oil tank such as a petroleum tankburied underground or a tank for various types of liquefied chemicals.

BACKGROUND ART

Various types of flow rate sensors (or flow velocity sensors) whichmeasure flow rates (or flow velocities) of various types of fluids,especially liquids, have heretofore been used, and so-called heat type(especially indirectly-heated type) flow rate sensors have been used fora reason that prices are easily reduced.

As the indirectly-heated flow rate sensor, a sensor has been used inwhich a sensor chip obtained by stacking a thin-film heating element anda thin-film temperature detecting element via an insulating layer usinga thin-film technique on a substrate is disposed in such a manner thatheat can be transferred between the sensor chip and the fluid in apiping which is a fluid channel. When the heating element is energized,the temperature detecting element is heated, and values of electricproperties such as electric resistances of the temperature detectingelement are changed. The change of the electric resistance value (basedon a temperature rise of the temperature detecting element) changes inaccordance with the flow rate (flow velocity) of the fluid flowing inthe piping. This is because a part of an amount of generated heat of theheating element is transferred into the fluid, the amount of the heatdiffusing in the fluid changes in accordance with the flow rate (flowvelocity) of the fluid, the amount of heat supplied into the temperaturedetecting element accordingly changes, and the electric resistance valueof the temperature detecting element changes. The change of the electricresistance value of the temperature detecting element differs also at atemperature of the fluid. Therefore, a temperature detector fortemperature compensation is incorporated in an electric circuit whichmeasures the change of the electric resistance value of the temperaturedetecting element, and changes of flow rate measurement by thetemperature of the fluid are reduced as much as possible.

This type of indirectly-heated flow rate sensor using the thin-filmelements is described, for example, in JP(A)-11-118566. In the flow ratesensor, an electric circuit including a bridge circuit is used in orderto obtain an electric output corresponding to the flow rate of thefluid.

Additionally, in recent years, importance of detection of leakage of thefluids from tanks or piping systems has increased. For example, when theoil leakages are generated from tanks of fuel oils such as gasoline,light oil, and kerosene, and a large amount of oil continuously leaks,problems such as fire breakout, environmental pollution, and resourceloss are caused, and it is therefore extremely preferable to detect oilleakage generation in an initial stage. Therefore, oil leakage detectionis sometimes required, for example, by a trace amount of 1 milliliter/hor less.

It is considered that the above-described indirectly-heated flow ratesensor is used in the detection of the oil leakage. However, in the flowrate sensor, the change of the output of the electric circuit withrespect to a flow rate change is reduced in a region in which a flowrate value is a trace amount of 1 milliliter/h or less, there is aproblem that an error of the flow rate measurement increases (i.e., aratio of a distinguishable flow rate difference increases duringmeasurement, and measurement sensitivity drops).

On the other hand, as the flow rate sensor, there is atwo-constant-point temperature difference detecting system in which afluid is heated by a heat source disposed in a specific position of apiping, temperature detecting elements are disposed at appropriatedistances on upstream and downstream sides of a heat source positionconcerning fluid circulation in the piping, and a fluid flow rate ismeasured based on a detected temperature difference between upstream anddownstream temperature detecting elements generated during thecirculation of the fluid in the piping. However, in a case where thesensor is used in the detection of the oil leakage, when the flow ratevalue is, for example, 3 milliliters/h or more, the change of the outputof the electric circuit with respect to the flow rate change is small,and therefore there is a problem that the error increases in a largeflow rate value region (i.e., the ratio of the distinguishable flow ratedifference increases during the measurement, and the measurementsensitivity drops).

Furthermore, the fuel oil tanks in a gas station and the like haveheretofore been buried underground in most cases, and the piping whichpumps out the fuel oil from the underground tank has also been buriedunderground. Micro cracks are generated in the piping by timedegradation before long, and there is a very strong possibility that oilleakage is generated from the cracks. In this situation, surroundingenvironment pollution is caused, and enormous expenses are required forrecovery. Therefore, the underground burial piping connected to theunderground tank is periodically inspected for presence of oil leakage(or the crack in the piping, which is a cause for the leakage).

As a method which has heretofore been used for this piping inspection,there has been a method in which a gas such as air or a liquid such aswater is pressurized/injected into the piping in a sealed state of thepiping, and the presence of a pressure drop after elapse of apredetermined time is detected. Conversely, there has also been a methodin which the tank is decompressed in a sealed state in the piping, andthe presence of pressure increase after the elapse of the predeterminedtime is detected. However, in these methods, an operation for sealingall openings in the piping with putty or the like is required prior tothe leakage inspection operation, an operation for extracting all theoil in the piping is required, and the operations are very troublesome.Additionally, when the openings are not completely sealed, the leakagedetected in these methods does not necessarily reflect actual oilleakage based on the cracks in the piping, and it cannot be said thatprecision is high for labors of the inspection operation.

To quickly cope with the leakage of the liquid in the piping, it isessential that the leakage can be detected at an early stage at whichthe cracks in the piping and the like are small and the leakage islittle, and therefore there has been a demand for the detection of asmall amount of leakage.

DISCLOSURE OF THE INVENTION

Therefore, an object of the present invention is to provide a method ofmeasuring a flow rate and a flowmeter in which the flow rate can bemeasured with satisfactory precision and sensitivity over a broad flowrate range from a trace flow rate region to a comparatively large flowrate region.

In order to attain the above object, according to the present invention,there is provided a method of measuring a flow rate of a fluid in afluid flow channel, comprising the steps of: obtaining a flow rate valueobtained by measuring a flow rate of the fluid by indirectly-heatedconstant-temperature controlling flow rate measuring as a measurementwith respect to a high flow rate region larger than a boundary flow rateregion predetermined concerning a value of the flow rate; obtaining aflow rate value obtained by two-constant-point temperature differencedetecting flow rate measuring as a measurement with respect to a lowflow rate region smaller than the boundary flow rate region; obtaining aflow rate value obtained by the indirectly-heated constant-temperaturecontrolling flow rate measuring or a flow rate value obtained by thetwo-constant-point temperature difference detecting flow rate measuringas a measurement with respect to the boundary flow rate region; andusing a measuring section for the indirectly-heated constant-temperaturecontrolling flow rate measuring as a heat source which heats the fluidin the fluid flow channel in the two-constant-point temperaturedifference detecting flow rate measuring.

In an aspect of the present invention, the boundary flow rate region isconstituted of one specific flow rate value only. In an aspect of thepresent invention, the method further comprises the steps of: firstmeasuring the flow rate of the fluid by the indirectly-heatedconstant-temperature controlling flow rate measuring; obtaining the flowrate value as the measurement, when the obtained flow rate value belongsto the high flow rate region or one of the high flow rate region and theboundary flow rate region; in another case, next measuring the flow rateof the fluid by the two-constant-point temperature difference detectingflow rate measuring; and obtaining the obtained flow rate value as themeasurement. In an aspect of the present invention, the method furthercomprises the steps of: first measuring the flow rate of the fluid bythe two-constant-point temperature difference detecting flow ratemeasuring; obtaining the flow rate value as the measurement, when theobtained flow rate value belongs to the low flow rate region or one ofthe low flow rate region and the boundary flow rate region; in anothercase, next measuring the flow rate of the fluid by the indirectly-heatedconstant-temperature controlling flow rate measuring; and obtaining theobtained flow rate value as the measurement.

In order to attain the above object, according to the present invention,there is also provided a flowmeter which measures a flow rate of a fluidin a fluid flow channel, comprising:

an indirectly-heated constant-temperature controlling flow ratemeasuring section and a two-constant-point temperature differencedetecting flow rate measuring section disposed facing the fluid flowchannel; and a computing section which obtains a measurement based on afirst flow rate corresponding output obtained using theindirectly-heated constant-temperature controlling flow rate measuringsection and a second flow rate corresponding output obtained using thetwo-constant-point temperature difference detecting flow rate measuringsection, wherein the indirectly-heated constant-temperature controllingflow rate measuring section has a heating element and a firsttemperature detecting element disposed adjacent to the heating element,the heating element is feedback-controlled based on a detectedtemperature of the first temperature detecting element, and the firstflow rate corresponding output is obtained based on a state of thefeedback control, the two-constant-point temperature differencedetecting flow rate measuring section has a second temperature detectingelement and a third temperature detecting element disposed on upstreamand downstream sides, respectively, of the indirectly-heatedconstant-temperature controlling flow rate measuring section withrespect to a fluid flowing direction in the fluid flow channel, and asecond flow rate corresponding output is obtained based on a differencebetween detected temperatures of the second and third temperaturedetecting elements, and

-   -   the computing section outputs a flow rate value obtained based        on the first flow rate corresponding output as a measurement        with respect to a high flow rate region larger than a boundary        flow rate region predetermined concerning the value of the flow        rate, outputs a flow rate value obtained based on the second        flow rate corresponding output as a measurement with respect to        a low flow rate region smaller than the boundary flow rate        region, and outputs a flow rate value obtained based on the        first or second flow rate corresponding output as a measurement        with respect to the boundary flow rate region.

In an aspect of the present invention, the boundary flow rate region isconstituted of one specific flow rate value only. In an aspect of thepresent invention, the computing section first outputs the flow ratevalue obtained based on the first flow rate corresponding output as themeasurement, when the first flow rate corresponding output correspondsto the high flow rate region or one of the high flow rate region and theboundary flow rate region, and, in another case, outputs the flow ratevalue obtained based on the second flow rate corresponding output as themeasurement. In an aspect of the present invention, the computingsection first outputs the flow rate value obtained based on the secondflow rate corresponding output as the measurement, when the second flowrate corresponding output corresponds to the low flow rate region or oneof the low flow rate region and the boundary flow rate region, and, inanother case, outputs the flow rate value obtained based on the firstflow rate corresponding output as the measurement.

In an aspect of the present invention, both the heating element and thefirst temperature detecting element have energizeable thin film shapes,and are stacked via an electrically insulating thin film. In an aspectof the present invention, the first flow rate corresponding output isobtained from a detection circuit including the heating element, thefirst temperature detecting element, and a temperature detecting elementfor temperature compensation.

Another object of the present invention is to provide a flow ratemeasuring section package and a flow rate measuring unit using the samefor measuring a flow rate in which the flow rate can be measured withsatisfactory precision and sensitivity over a broad flow rate range froma trace flow rate region to a comparatively large flow rate region.

In order to attain the above object, according to the present invention,there is provided a flow rate measuring section package for measuring aflow rate of a fluid in a fluid flow channel, comprising:

-   -   an indirectly-heated constant-temperature controlling flow rate        measuring section and a two-constant-point temperature        difference detecting flow rate measuring section which are        attached to the fluid flow channel, the two-constant-point        temperature difference detecting flow rate measuring section        comprising an upstream-side temperature detecting section and a        downstream-side temperature detecting section disposed on        upstream and downstream sides, respectively, of the        indirectly-heated constant-temperature controlling flow rate        measuring section with respect to a fluid flowing direction in        the fluid flow channel;    -   wherein the indirectly-heated constant-temperature controlling        flow rate measuring section has a heating element and a first        temperature detecting element disposed adjacent to the heating        element, the upstream-side temperature detecting section has a        second temperature detecting element, and the downstream-side        temperature detecting section has a third temperature detecting        element, and    -   the indirectly-heated constant-temperature controlling flow rate        measuring section is connected to a first wiring section for        electric connection to the heating element and the first        temperature detecting element, the upstream-side temperature        detecting section is connected to a second wiring section for        electric connection to the second temperature detecting element,        and the downstream-side temperature detecting section is        connected to a third wiring section for electric connection to        the third temperature detecting element.

In an aspect of the present invention, one of the first, second, andthird wiring sections are all formed using flexible wiring substrates.In an aspect of the present invention, the indirectly-heatedconstant-temperature controlling flow rate measuring section, theupstream-side temperature detecting section, the downstream-sidetemperature detecting section, and a part of the fluid flow channel towhich these sections are attached are housed in a casing. In an aspectof the present invention, first, second, and third terminalsconstituting the first, second, and third wiring sections, respectively,are extended from the casing.

In an aspect of the present invention, a temperature detecting sectionhaving a temperature detecting element for temperature compensation isaccommodated in the casing, the temperature detecting section isconnected to a heat transfer member extending out of the casing, and afourth terminal constituting a fourth wiring for electric connection tothe temperature detecting element for temperature compensation isextended from the casing. In an aspect of the present invention, boththe heating element and the first temperature detecting element haveenergizeable thin film shapes, and are stacked via an electricallyinsulating thin film.

In order to attain the above object, according to the present invention,there is also provided a flow rate measuring unit, comprising: theabove-mentioned flow rate measuring section package; a unit substratefor attaching the flow rate measuring section package; and a flow ratemeasuring circuit element attached to the unit substrate.

In an aspect of the present invention, the flow rate measuring circuitelement includes an analog circuit element, which feedback-controls theheating element based on a detected temperature of the first temperaturedetecting element, obtains a first flow rate corresponding output basedon a state of the feedback control, and obtains a second flow ratecorresponding output based on a difference between detected temperaturesof the second and third temperature detecting elements.

In an aspect of the present invention, the flow rate measuring circuitelement further includes a digital circuit element, which comprises acomputing section which obtains a flow rate measurement based on thefirst and second flow rate corresponding outputs, and the computingsection outputs a flow rate value obtained based on the first flow ratecorresponding output as the measurement with respect to a high flow rateregion larger than a boundary flow rate region predetermined concerningthe value of the flow rate, outputs a flow rate value obtained based onthe second flow rate corresponding output as the measurement withrespect to a low flow rate region smaller than the boundary flow rateregion, and outputs a flow rate value obtained based on the first orsecond flow rate corresponding output as the measurement with respect tothe boundary flow rate region.

In an aspect of the present invention, the boundary flow rate region isconstituted of one specific flow rate value only. In an aspect of thepresent invention, the computing section first outputs the flow ratevalue obtained based on the first flow rate corresponding output as themeasurement, when the first flow rate corresponding output correspondsto the high flow rate region or one of the high flow rate region and theboundary flow rate region, and, in another case, outputs the flow ratevalue obtained based on the second flow rate corresponding output as themeasurement, or, first outputs the flow rate value obtained based on thesecond flow rate corresponding output as the measurement, when thesecond flow rate corresponding output corresponds to the low flow rateregion or one of the low flow rate region and the boundary flow rateregion, and, in another case, outputs the flow rate value obtained basedon the first flow rate corresponding output as the measurement.

Still another object of the present invention is to provide a pipingleakage inspection apparatus or device capable of easily and correctlydetecting even a trace amount of leakage. Furthermore object of thepresent invention is to provide a leakage inspection apparatus or devicecapable of performing leakage inspection utilizing a liquid which hasbeen transferred into a piping and which is left in the piping.

In order to attain the above object, according to the present invention,there is provided a piping leakage inspection apparatus which inspects aleakage of a liquid from a piping to be measured, comprising:

-   -   an internal piping system comprising a connection end for        communication with the piping to be measured, and a liquid        discharge end; a tank for temporarily storing a pressurized        liquid, which is connected to the internal piping system; and a        pump and a flowmeter disposed in order in a path extending to        the connection end from the tank for temporarily storing the        pressurized liquid in the internal piping system,    -   wherein the internal piping system is capable of forming a first        path which transfers the liquid into the tank for temporarily        storing the pressurized liquid from the piping to be measured        through the connection end by the pump without passing the        liquid through the flowmeter, a second path for pressure-feeding        the liquid into the piping to be measured from the tank for        temporarily storing the pressurized liquid through the flowmeter        and the connection end by the pump, and a third path for        transferring the liquid into the liquid discharge end from the        tank for temporarily storing the pressurized liquid by the pump,        and    -   the leakage of the liquid from the piping to be measured is        inspected based on a liquid flow rate detected by the flowmeter        at a time when a liquid pressure of a part of the second path        extending to the connection end from the pump is raised by the        liquid pressure-feeding by the pump in a state in which the        connection end is connected to the piping to be measured.

In an aspect of the present invention, the internal piping system iscapable of forming a fourth path which returns the liquid into the tankfor temporarily storing the pressurized liquid from a part between thepump and the flowmeter in a case where the liquid pressure of the partextending to the connection end from the pump exceeds a set value in thesecond path. In an aspect of the present invention, the internal pipingsystem is further capable of forming a fifth path for releasing theliquid pressure of at least a part of the part extending to theconnection end from the flowmeter in the second path.

In an aspect of the present invention, the flowmeter comprises: anindirectly-heated constant-temperature controlling flow rate measuringsection and a two-constant-point temperature difference detecting flowrate measuring section disposed facing a fluid flow channel constitutingthe internal piping system; and a computing section which obtains ameasurement based on a first flow rate corresponding output obtainedusing the indirectly-heated constant-temperature controlling flow ratemeasuring section and a second flow rate corresponding output obtainedusing the two-constant-point temperature difference detecting flow ratemeasuring section,

-   -   the indirectly-heated constant-temperature controlling flow rate        measuring section has a heating element and a first temperature        detecting element disposed adjacent to the heating element, the        heating element is feedback-controlled based on a detected        temperature of the first temperature detecting element, and the        first flow rate corresponding output is obtained based on a        state of the feedback control,    -   the two-constant-point temperature difference detecting flow        rate measuring section has a second temperature detecting        element and a third temperature detecting element disposed on        upstream and downstream sides, respectively, of the        indirectly-heated constant-temperature controlling flow rate        measuring section with respect to a fluid flowing direction in        the fluid flow channel, and the second flow rate corresponding        output is obtained based on a difference between detected        temperatures of the second and third temperature detecting        elements, and    -   the computing section outputs a flow rate value obtained based        on the first flow rate corresponding output as a measurement        with respect to a high flow rate region larger than a boundary        flow rate region predetermined concerning the value of the flow        rate, outputs a flow rate value obtained based on the second        flow rate corresponding output as a measurement with respect to        a low flow rate region smaller than the boundary flow rate        region, and outputs a flow rate value obtained based on the        first or second flow rate corresponding output as a measurement        with respect to the boundary flow rate region.

In an aspect of the present invention, the boundary flow rate region isconstituted of one specific flow rate value only. In an aspect of thepresent invention, the computing section first outputs the flow ratevalue obtained based on the first flow rate corresponding output as themeasurement, when the first flow rate corresponding output correspondsto the high flow rate region or one of the high flow rate region and theboundary flow rate region, and, in another case, outputs the flow ratevalue obtained based on the second flow rate corresponding output as themeasurement. In an aspect of the present invention, the computingsection first outputs the flow rate value obtained based on the secondflow rate corresponding output as the measurement, when the second flowrate corresponding output corresponds to the low flow rate region or oneof the low flow rate region and the boundary flow rate region, and, inanother case, outputs the flow rate value obtained based on the firstflow rate corresponding output as the measurement.

In an aspect of the present invention, both the heating element and thefirst temperature detecting element have energizeable thin film shapes,and are stacked via an electrically insulating thin film. In an aspectof the present invention, the first flow rate corresponding output isobtained from a detection circuit including the heating element, thefirst temperature detecting element, and a temperature detecting elementfor temperature compensation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view showing an embodiment of aflowmeter according to the present invention, for use in performing amethod of measuring a flow rate according to the present invention;

FIG. 2 is a partial perspective view showing a structure of theflowmeter of FIG. 1;

FIG. 3 is a partial sectional view of FIG. 2;

FIG. 4 is a partial sectional view of FIG. 2;

FIG. 5 is a block diagram showing a flow rate measuring system of theflowmeter of FIG. 1;

FIG. 6 is a diagram showing a circuit constitution for detecting a flowrate of the flowmeter of FIG. 1;

FIG. 7 is a diagram showing an example of a calibration curve forconversion of Vh;

FIG. 8 is a diagram showing an example of the calibration curve for theconversion of Vout;

FIG. 9 is a schematic diagram showing one embodiment of a liquid leakagemonitoring system using a method of measuring the flow rate and theflowmeter according to the present invention;

FIG. 10 is a partially omitted perspective view showing an embodiment ofa flow rate measuring section package according to the presentinvention;

FIG. 11A is a plan view of the flow rate measuring section package ofFIG. 10;

FIG. 11B is a plan view of the flow rate measuring section package ofFIG. 10;

FIG. 12A is a transversely sectional view of the flow rate measuringsection package of FIG. 10;

FIG. 12B is a vertically sectional view of the flow rate measuringsection package of FIG. 10;

FIG. 13A is a plan view showing an embodiment of the flow rate measuringsection package according to the present invention;

FIG. 13B is a front view showing an embodiment of the flow ratemeasuring section package according to the present invention;

FIG. 14A is a transversely sectional view of the flow rate measuringsection package of FIGS. 13A and 13B;

FIG. 14B is a vertically sectional view of the flow rate measuringsection package of FIGS. 13A and 13B;

FIG. 15 is a perspective view showing an embodiment of a flow ratemeasuring unit according to the present invention;

FIG. 16A is a plan view of the flow rate measuring unit of FIG. 15;

FIG. 16B is a front view of the flow rate measuring unit of FIG. 15;

FIG. 16C is a side view of the flow rate measuring unit of FIG. 15;

FIG. 17 is a perspective view showing an embodiment of the flow ratemeasuring unit according to the present invention;

FIG. 18A is a plan view of the flow rate measuring unit of FIG. 17;

FIG. 18B is a front view of the flow rate measuring unit of FIG. 17;

FIG. 18C is a side view of the flow rate measuring unit of FIG. 17;

FIG. 19 is a perspective view showing an embodiment of the flow ratemeasuring unit according to the present invention;

FIG. 20A is a plan view of the flow rate measuring unit of FIG. 19;

FIG. 20B is a front view of the flow rate measuring unit of FIG. 19;

FIG. 20C is a side view of the flow rate measuring unit of FIG. 19;

FIG. 21 is a sectional view showing an embodiment of incorporation ofthe flow rate measuring section package according to the presentinvention into the flowmeter;

FIG. 22 is a sectional view showing an embodiment of incorporation ofthe flow rate measuring unit according to the present invention into theflowmeter;

FIG. 23 is a diagram showing one embodiment of a piping leakageinspection apparatus according to the present invention;

FIG. 24 is an explanatory view of an operation of the apparatus of FIG.23;

FIG. 25 is an explanatory view of the operation of the apparatus of FIG.23;

FIG. 26 is an explanatory view of the operation of the apparatus of FIG.23;

FIG. 27 is an explanatory view of the operation of the apparatus of FIG.23;

FIG. 28 is a diagram showing one embodiment of the piping leakageinspection apparatus according to the present invention;

FIG. 29 is an explanatory view of the operation of the apparatus of FIG.28;

FIG. 30 is an explanatory view of the operation of the apparatus of FIG.28;

FIG. 31 is an explanatory view of the operation of the apparatus of FIG.28;

FIG. 32 is an explanatory view of the operation of the apparatus of FIG.28;

FIG. 33 is a diagram showing one embodiment of the piping leakageinspection apparatus according to the present invention;

FIG. 34 is an explanatory view of the operation of the apparatus of FIG.33;

FIG. 35 is an explanatory view of the operation of the apparatus of FIG.33;

FIG. 36 is an explanatory view of the operation of the apparatus of FIG.33;

FIG. 37 is an explanatory view of the operation of the apparatus of FIG.33;

FIG. 38 is a diagram showing one embodiment of the piping leakageinspection apparatus according to the present invention;

FIG. 39 is an explanatory view of the operation of the apparatus of FIG.38;

FIG. 40 is an explanatory view of the operation of the apparatus of FIG.38;

FIG. 41 is an explanatory view of the operation of the apparatus of FIG.38;

FIG. 42 is an explanatory view of the operation of the apparatus of FIG.38;

FIG. 43 is a schematic sectional view showing one embodiment of aflowmeter for use in the piping leakage inspection apparatus accordingto the present invention; and

FIG. 44 is a schematic diagram showing one embodiment of a liquidleakage monitoring system in which the piping leakage inspectionapparatus according to the present invention is used.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described hereinafter withreference to the drawings. Corresponding parts, members, or devices overthe drawings are denoted with the same reference numerals.

FIG. 1 is a schematic sectional view showing an embodiment of aflowmeter according to the present invention, for use in performing amethod of measuring a flow rate according to the present invention, FIG.2 is a partial perspective view showing a structure of the flowmeter,FIGS. 3 and 4 are partial sectional views of FIG. 2, FIG. 5 is a blockdiagram showing a flow rate measuring system of the present embodiment,and FIG. 6 is a diagram showing a circuit constitution for detecting aflow rate of the system. The present embodiment is used in detecting aleakage of a liquid in a tank from the tank.

As shown in FIG. 1, a lower part of a cylindrical measuring tube 12 isimmersed in an in-tank liquid (inflammable liquids such as gasoline,light oil, and kerosene) 2. An upper end portion of the measuring tube12 opens into the atmosphere, and a lower end portion thereof opens inthe in-tank liquid 2. In the measuring tube, a fine measuring tube 14extending in a vertical direction is disposed in a position which is alittle above the lower end portion of the measuring tube 12, and thein-tank liquid 2 passes through the fine measuring tube 14. In thepresent embodiment, the fine measuring tube 14 is used as a fluidchannel. In a case where the leakage of the in-tank liquid 2 isgenerated, under conditions that the liquid is not replenished into thetank or the liquid is not pumped out of the tank, as shown, a liquidlevel of the in-tank liquid 2 drops below that in the measuring tube 12,and the liquid passes downwards passes through the fine measuring tube14 based on the drop. When a sectional area of the fine measuring tube14 is set to be sufficiently small (e.g., {fraction (1/50)} or less,{fraction (1/100)} or less, further {fraction (1/300)} or less) withrespect to that of the measuring tube 12, the liquid can be passedthrough the fine measuring tube 14 to such an extent that the flow ratecan be measured even during a little liquid leakage.

As shown in FIG. 1, an indirectly-heated constant-temperaturecontrolling flow rate measuring section 16 and a two-constant-pointtemperature difference detecting flow rate measuring section 18 aredisposed facing the fine measuring tube 14. The two-constant-pointtemperature difference detecting flow rate measuring section 18 hastemperature detecting sections 18 a, 18 b disposed on upper and lowersides of the indirectly-heated constant-temperature controlling flowrate measuring section 16. A temperature detecting section 20 fordetecting the temperature of the liquid in the measuring tube 12 isdisposed.

As shown in FIGS. 2 and 3, the fine measuring tube 14 extends throughthe indirectly-heated constant-temperature controlling flow ratemeasuring section 16. The indirectly-heated constant-temperaturecontrolling flow rate measuring section 16 has a heat transfer member161 brought into contact with the outer face of the fine measuring tube14, a thin-film temperature detecting element or heat sensing element(first temperature detecting element) 162 bonded to the heat transfermember 161, and a thin-film heating element 163 stacked on the thin-filmtemperature detecting element 162 via an electrically insulating thinfilm 164. The thin-film temperature detecting element 162 and thin-filmheating element 163 are formed into required patterns, and electrodesfor energizing the elements are connected to wirings 162′, 163′. Theheat transfer member 161 is formed of a metal or an alloy, for example,having a thickness of 0.2 mm and a width of about 2 mm.

It is to be noted that these thin-film temperature detecting element162, electrically insulating thin film 164, and thin-film heatingelement 163 may be deposited/formed on a support substrate disposed onthe side of the thin-film heating element 163, and bonded, together withthe support substrate, to the heat transfer member 161 facing the heattransfer member on the side of the thin-film temperature detectingelement 162. As the above-described support substrate, for example, arectangular substrate formed of silicon, alumina or the like and havinga thickness of about 0.4 mm and about 2 mm squares can be used.

The wirings 162′, 163′ are connected to a wiring (not shown) formed on awiring substrate 24 such as a flexible wiring substrate. The heattransfer member 161, thin-film temperature detecting element 162,electrically insulating thin film 164, thin-film heating element 163,and wirings 1621, 1631 are sealed together with a part of the wiringsubstrate 24 and a part of the fine measuring tube 14 by a sealingmember 22 formed of a synthetic resin.

As shown in FIGS. 2 and 4, the fine measuring tube 14 extends throughone temperature detecting section 18 a of the two-constant-pointtemperature difference detecting flow rate measuring section. Thetemperature detecting section 18 a has a heat transfer member 181brought into contact with the outer face of the fine measuring tube 14,and a thin-film temperature detecting element (second temperaturedetecting element) 182 bonded to the heat transfer member 181. Thethin-film temperature detecting element 182 is formed into a requiredpattern, and an electrode for energizing the element is connected to awiring 182′. The heat transfer member 181 is formed of a metal or analloy, for example, having a thickness of 0.2 mm and a width of about 2mm in the same manner as in the heat transfer member 161. It is to benoted that the thin-film temperature detecting element 182 formed on thesupport substrate as described above may be bonded, together with thesupport substrate, to the heat transfer member 181 in such a manner asto face the member on the side of the thin-film temperature detectingelement 182.

The wiring 182′ is connected to a wiring (not shown) formed on thewiring substrate 24. The heat transfer member 181, thin-film temperaturedetecting element 182, and wiring 182′ are sealed together with a partof the temperature detecting section 20 and a part of the fine measuringtube 14 by a sealing member 23 formed of a synthetic resin.

The other temperature detecting section 18 b of the two-constant-pointtemperature difference detecting flow rate measuring section has aconstitution similar to that of the temperature detecting section 18 a,and is sealed together with a part of the wiring substrate 24 and a partof the fine measuring tube 14 by the sealing member formed of thesynthetic resin. Additionally, an element of the temperature detectingsection 18 a, corresponding to a thin-film temperature detecting elementfunctioning as the second temperature detecting element, functions as athird temperature detecting element in the temperature detecting section18 b.

The thin-film temperature detecting element 162, thin-film heatingelement 163, and wirings 162′, 163′ for the elements in theindirectly-heated constant-temperature controlling flow rate measuringsection 16, and further the temperature detecting section 20 constitutea first detection circuit 30 of FIG. 5. The thin-film temperaturedetecting element (second temperature detecting element) 182 of thetemperature detecting section 18 a, and the thin-film temperaturedetecting element (third temperature detecting element) of thetemperature detecting section 18 b in the two-constant-point temperaturedifference detecting flow rate measuring section constitute a seconddetection circuit 32 of FIG. 5. An output (hereinafter referred to as“flow rate value output” or “flow rate corresponding output” Vhcorresponding to a flow rate value of the indirectly-heatedconstant-temperature controlling flow rate measuring is output from thefirst detection circuit 30, and an output (hereinafter referred tosimply as “flow rate value output” Vout corresponding to the flow ratevalue of the two-constant-point temperature difference detecting flowrate measuring is output from the second detection circuit 32. Theseflow rate value outputs are input into a computing section 34 shown inFIG. 5.

As shown in FIG. 6, in the first detection circuit 30 for obtaining theflow rate value output Vh a direct-current voltage input Vin from apower supply circuit (not shown) is supplied to a bridge circuit 40. Thebridge circuit 40 includes a temperature detecting section Rf includingthe thin-film temperature detecting element 162, the temperaturedetecting section 20 (Rc) including the thin-film temperature detectingelement for temperature compensation, resistance elements AR, R1, and avariable resistance element R2. Potentials Va, Vb of points a, b of thebridge circuit 40 are input into a differential amplification circuit42. It is to be noted that the differential amplification circuit 42preferably includes a variable resistance element, an integrationcircuit and the like for adjusting response characteristics of feedbackcontrol described below.

On the other hand, the input Vin is supplied to the thin-film heatingelement 163 via a transistor 44 for controlling a current supplied tothe heating element Rh including the thin-film heating element 163. Anoutput of the differential amplification circuit 42 is input into acontrol input terminal (gate) of the transistor 44. That is, in theindirectly-heated constant-temperature controlling flow rate measuringsection 16, the temperature detection by the thin-film temperaturedetecting element 162 is executed based on the heating of the thin-filmheating element 163 under an influence of heat absorption by the liquidvia the heat transfer member 161. Moreover, as a result of thetemperature detection, a difference between the potentials Va, Vb of thepoints a, b of the bridge circuit 40 shown in FIG. 6 is obtained.

A value of (Va-Vb) changes, when the temperature of the temperaturedetecting element 162 changes in accordance with the flow rate of thefluid. When the resistance values of the resistance elements AR, R1 andthe variable resistance element R2 of the bridge circuit 40 areappropriately set beforehand, the value of (Va-Vb) can be zeroed with adesired fluid flow rate which is a reference. In the reference flowrate, the output of the differential amplification circuit 42 becomesconstant (value corresponding to the reference flow rate), and theresistance value of the transistor 44 is also constant. In this case, adivided voltage applied to the thin-film heating element 163 is alsoconstant, and the voltage output Vh at this time indicates the referenceflow rate.

When the fluid flow rate increases/decreases, polarity (which differswith positive/negative resistance-temperature characteristics of thetemperature detecting element 162) and magnitude of the output of thedifferential amplification circuit 42 change in accordance with thevalue of (Va-Vb), and accordingly the output of the differentialamplification circuit 42 changes.

When the fluid flow rate increases, the temperature of the temperaturedetecting element 162 drops, and therefore the differentialamplification circuit 42 controls an input with respect to a gate of thetransistor 44 in such a manner as to decrease the resistance value ofthe transistor 44, so that a heating value of the thin-film heatingelement 163 is increased (i.e. power is increased).

On the other hand, when the fluid flow rate decreases, the temperatureof the temperature detecting element 162 rises, and therefore thedifferential amplification circuit 42 controls an input with respect tothe gate of the transistor 44 in such a manner as to increase theresistance value of the transistor 44, so that the heating value of thethin-film heating element 163 is decreased (i.e. power is decreased).

As described above, the heating of the thin-film temperature detectingelement 162 is feedback-controlled regardless of the change of the fluidflow rate in such a manner that the temperature detected by thetemperature detecting element 162 indicates a target value. Moreover, inthis case, since the voltage applied to the thin-film heating element162 corresponds to the fluid flow rate, the voltage is taken as the flowrate value output Vh.

As described above, the indirectly-heated constant-temperaturecontrolling measuring is performed. In the indirectly-heatedconstant-temperature controlling measuring described in the presentinvention, the heating element is disposed adjacent to the firsttemperature detecting element, the heating element isfeedback-controlled based on a detected temperature (in actual, electriccharacteristics detected corresponding to the detected temperature) ofthe first temperature detecting element, and a first flow ratecorresponding output is obtained from a state of the feedback control.

Moreover, as shown in FIG. 6, in the second detection circuit 32 forobtaining the flow rate value output Vout, the direct-current voltageinput Vin is supplied to a bridge circuit 46. The bridge circuit 46includes the temperature detecting section 18 a (T1) including thethin-film temperature detecting element 182, the temperature detectingsection 18 b (T2) including the thin-film temperature detecting element,a resistance element R3, and a variable resistance element R4.Potentials Vc, Vd of points c, d of the bridge circuit 46 are input intoa differential amplifier circuit 48. When the resistance values of theresistance element R3 and variable resistance element R4 of the bridgecircuit 46 are appropriately set beforehand, a voltage outputcorresponding to a difference between detected temperatures of thetemperature detecting sections 18 a, 18 b can be obtained from thedifferential amplifier circuit 48.

As described above, in the indirectly-heated constant-temperaturecontrolling flow rate measuring section 16, heat is generated from thethin-film heating element 163, and a part of the heat is transferred tothe liquid via the heat transfer member 161, and utilized as a heatsource for heating the liquid. The temperature of the thin-filmtemperature detecting element (first temperature detecting element) 162is controlled to indicate a predetermined value, and the temperature canbe set to be lower than a flash point of the liquid. Therefore, theelement can be applied to the flow rate measuring of the inflammablefluid.

When the liquid does not passes therethrough, the detected temperatureof the temperature detecting section 18 a is equal to that of thetemperature detecting section 18 b. However, when the liquid passestherethrough, an influence of the liquid heating by the heat source isstronger on a downstream side than on an upstream side, and thereforethe detected temperature of the temperature detecting section 18 a isdifferent from that of the temperature detecting section 18 b. Since thevoltage output corresponding to the difference between the detectedtemperatures of the temperature detecting sections 18 a, 18 bcorresponds to the fluid flow rate, the output is set to the flow ratevalue output Vout.

As described above, two-constant-point temperature difference detectingflow rate measuring is performed. In the two-constant-point temperaturedifference detecting flow rate measuring, referred to in the presentinvention, a second flow rate corresponding output is obtained based onthe temperature difference (in actual, the difference of the electriccharacteristics detected in accordance with the detected temperaturedifference) detected by the second and third temperature detectingelements disposed on the upstream and downstream sides of theindirectly-heated constant-temperature controlling flow rate measuringsection, respectively.

Next, an operation of the computing section 34 will be described.

In the computing section 34, conversion into the corresponding flow ratevalue is performed using built-in calibration curves based on Vh andVout. FIG. 7 shows an example of the calibration curve for theconversion of Vh, and FIG. 8 shows an example of the calibration curvefor the conversion of Vout. As shown in these figures, a region in whichthe flow rate value is F1 or more and F2 or less is predetermined as aboundary flow rate region. The flow rate values F1, F2 which set upperand lower limits of the boundary flow rate region can be set to thevalues, for example, in a rage of 1 milliliter/h (mL/h) to 2milliliters/h (mL/h). A region whose flow rate value is less than F1 isset to a low flow rate region, and a region whose flow rate valueexceeds F2 is set to a high flow rate region. As shown in FIG. 7, in thecalibration curve for the conversion of Vh, an output corresponding tothe flow rate value F1 is set to Vh1, and an output corresponding to theflow rate value F2 is set to Vh2. As shown in FIG. 8, in the calibrationcurve for the conversion of Vout, an output corresponding to the flowrate value F1 is set to Vout1, and an output corresponding to the flowrate value F2 is set to Vout2.

In the computing section 34, the flow rate value obtained based on thefirst flow rate corresponding output Vh is output as a measurement withrespect to the high flow rate region, the flow rate value obtained basedon the second flow rate corresponding output Vout is output as ameasurement with respect to the low flow rate region, and the flow ratevalue obtained based on the first flow rate corresponding output Vh orthe second flow rate corresponding output Vout is output as ameasurement with respect to the boundary flow rate region.

Concretely, first the flow rate of the fluid is measured by theindirectly-heated constant-temperature controlling flow rate measuring(i.e., the flow rate value obtained based on the first flow ratecorresponding output Vh is obtained). When the obtained flow rate valuebelongs to the high flow rate region (i.e., the output Vh exceeds Vh2),the flow rate value is output as the measurement. In another case, theflow rate of the fluid is measured by the two-constant-point temperaturedifference detecting flow rate measuring (i.e., the flow rate valueobtained based on the second flow rate corresponding output Vout isobtained), and the obtained flow rate value is output as themeasurement. Alternatively, when the flow rate value obtained based onthe first flow rate corresponding output Vh belongs to one of the highflow rate region and the boundary flow rate region (i.e., the output Vhis Vh1 or more), the flow rate value is output as a measurement. Inanother case, the flow rate value obtained based on the second flow ratecorresponding output Vout may be output as the measurement.

In another method, first the flow rate of the fluid is measured by thetwo-constant-point temperature difference detecting flow rate measuring(i.e., the flow rate value obtained based on the second flow ratecorresponding output Vout is obtained). When the obtained flow ratevalue belongs to the low flow rate region (i.e., the output Vout is lessthan Vout1), the corresponding flow rate value is output as ameasurement. In another case, the flow rate of the fluid is measured bythe indirectly-heated constant-temperature controlling flow ratemeasuring (i.e., the flow rate value obtained based on the first flowrate corresponding output Vh is obtained), and the obtained flow ratevalue is output as a measurement. Alternatively, when the flow ratevalue obtained based on the second flow rate corresponding output Voutbelongs to one of the low flow rate region and the boundary flow rateregion (i.e., when the output Vout is Vout2 or less), the flow ratevalue is output as a measurement. In another case, the flow rate valueobtained based on the first flow rate corresponding output Vh may beoutput as a measurement.

In the present invention, the boundary flow rate region may beconstituted of a specific flow rate value only. This specific flow ratevalue corresponds to a case where F1 described above matches F2, and theabove description applies as such.

Integrating concerning time is appropriately performed based on the flowrate (momentary flow rate) measurement output from the computing section34, and an integrated flow rate can be calculated. The values of theobtained momentary flow rate and integrated flow rate can beappropriately displayed, appropriately stored in a memory, and furthertransmitted to a desired external device via an appropriatecommunication circuit.

As described above, the flow rate is measured. When the flow ratemeasurement exceeds a measurement error based on the flow ratemeasurement output from the computing section 34 as a result of the flowrate measuring, it is judged that there is a leakage of the in-tankliquid, and the leakage is detected. The leakage is preferably detected,for example, at night under conditions that any liquid is notreplenished into the tank or any liquid is pumped out of the tank. FIG.9 shows one embodiment of a liquid leakage monitoring system utilizingthe above-described leakage detection of the in-tank liquid, and furtherincluding the leakage detection of a piping system.

FIG. 9 shows a state in which the measuring tube 12 is inserteddownwards into the in-tank liquid 2 from a measuring port of theunderground-tank. It is to be noted that a communication hole (notshown) with outside air is formed in an upper part of the measuring tube12. A tank leakage detection device including the first detectioncircuit 30, second detection circuit 32, and computing section 34 isdisposed above the measuring tube 12. On the other hand, the tank isconnected to a buried piping in which the liquid pumped out of the tankpasses therethrough, and is provided with a piping leakage detectiondevice which detects the leakage of the liquid from the piping. In thepiping leakage detection device, the above-described flow rate measuringmethod and flowmeter according to the present invention can be used.

The tank leakage detection device and piping leakage detection deviceare connected to an individual monitoring apparatus disposed for eachtank by internal communication means via cable or radio in such a mannerthat signals can be transmitted/received. The individual monitoringapparatus periodically (e.g., once a day) inquires the tank leakagedetection device and the piping leakage detection device of detectionresults (presence of the leakage, a degree [flow rate] of the leakage,etc.). Leakage data obtained from the leakage detection device is storedin a memory of the individual monitoring apparatus. The data stored inthis memory is constituted of a part indicating tank leakage detectionresults, and a part indicating piping leakage detection results.

The individual monitoring apparatus is capable of transmitting/receivingsignals to/from a concentrated monitoring apparatus disposed for aplurality of tanks via communication means by a telephone circuit,internet, or leased circuit. The concentrated monitoring apparatusinquires a plurality of individual monitoring apparatuses of thedetection results stored in the memories of the individual monitoringapparatuses as needed. The leakage data obtained from the individualmonitoring apparatus is stored in the memory of the concentratedmonitoring apparatus, and is appropriately output by display andprinting. The data stored in the memory is constituted of a part of anidentification number of each individual monitoring apparatus (or theunderground tank monitored by the individual monitoring apparatus), apart indicating the corresponding tank leakage detection result, and apart indicating a piping leakage detection result.

The individual monitoring apparatus is installed in the same place asthat where the tank is installed or in the vicinity of the place, forexample, in a gas station office, facility management office, guardoffice or the like. It is to be noted that functions of theabove-described individual monitoring apparatuses with respect to aplurality of tanks may be integrated to constitute one compositemonitoring apparatus. The leakage data stored in the individualmonitoring apparatus or composite monitoring apparatus can be directlyread and displayed from the monitoring apparatus. On the other hand, theconcentrated monitoring apparatus can be disposed in a positionunrelated to the position of each tank, such as a concentratedmanagement center, a public inspection institution, or the like.

A flow rate measuring section package and a flow rate measuring unitaccording to the present invention are usable in the flowmeter describedabove with reference to FIGS. 1 to 9. In this case, the temperaturedetecting section 18 a is an upstream-side temperature detectingsection, and the temperature detecting section 18 b is a downstream-sidetemperature detecting section. The first detection circuit 30 and thesecond detection circuit 32 are also included to constitute an analogcircuit. The flow rate value outputs Vh, Vout of the analog circuit areinput into the computing section 34 shown in FIG. 5. The computingsection 34 is included to constitute a digital circuit.

FIG. 10 is a partially omitted perspective view showing anotherembodiment of the flow rate measuring section package according to thepresent invention, FIGS. 11A and 11B are a plan view and a front view ofthe package, and FIGS. 12A and 12B are a transversely sectional view anda vertically sectional view of the package.

In the present embodiment, an indirectly-heated constant-temperaturecontrolling flow rate measuring section 16, an upstream-side temperaturedetecting section 18 a, a downstream-side temperature detecting section18 b, and a part of a fluid channel 14 to which they are attached areaccommodated in a casing 100. First terminals 116 constituting firstwiring sections electrically connected to a thin-film heating element163 and a thin-film temperature detecting element 162 of theindirectly-heated constant-temperature controlling flow rate measuringsection 16 are extended outwards from the casing 100. Second terminals118 a constituting second wiring sections electrically connected to athin-film temperature detecting element 182 of the upstream-sidetemperature detecting section 18 a are extended outwards from the casing100. Similarly, third terminals 118 b constituting third wiring sectionselectrically connected to the thin-film temperature detecting element ofthe downstream-side temperature detecting section 18 b are extendedoutwards from the casing 100.

Furthermore, a temperature detecting section 20 having a temperaturedetecting element for temperature compensation is accommodated in thecasing 100, and the temperature detecting section 20 is connected to aheat transfer member 201 extending out of the casing 100. In theabove-described embodiment of FIG. 1, the temperature detecting section20 is used in which the heat transfer member extends into the liquid inorder to detect the temperature of the liquid as an environmenttemperature. However, in the present embodiment, the temperaturedetecting section 20 detects an ambient air temperature of the casing100 as the environment temperature. Moreover, in the casing 100, fourthterminals 120 constituting four wiring sections electrically connectedto the temperature detecting element for temperature compensation areextended outwards from the casing 100.

In the present embodiment, as shown in FIG. 12A, the first to fourthterminals are connected to predetermined thin-film heating elements orthin-film temperature detecting elements of the indirectly-heatedconstant-temperature controlling flow rate measuring section 16,upstream-side temperature detecting section 18 a, downstream-sidetemperature detecting section 18 b, and temperature detecting section 20via bonding wires.

FIGS. 13A and 13B are a plan view and a front view showing still anotherembodiment of the flow rate measuring section package according to thepresent invention, and FIGS. 14A and 14B are a transversely sectionalview and a vertically sectional view of the package, respectively. Thepresent embodiment is different from the above-described embodiment ofFIGS. 10 to 12B in that the temperature detecting section 20, heattransfer member 201, and fourth terminals 120 are not disposed. Thepresent embodiment is provided with preliminary terminals 130 formounting the flow rate measuring unit described later onto a unitsubstrate. Some of the preliminary terminals 130 can be used forwirings.

FIG. 15 is a perspective view showing an embodiment of the flow ratemeasuring unit according to the present invention, and FIGS. 16A, 16B,and 16C are a plan view, a front view, and a side view of the unit,respectively. In the present embodiment, a flow rate measuring sectionpackage 200 of FIGS. 10 to 12B, described above, is attached to a unitsubstrate 220 in such a manner that the first to fourth terminals extendparallel with respect to the unit substrate 220 on which a requiredcircuit is formed, and further an analog circuit element 222constituting a flow rate measuring circuit element is attached to theunit substrate 220. Accordingly, the first detection circuit 30 and thesecond detection circuit 32 shown in FIGS. 5 and 6 are formed. The flowrate measuring circuit element may further include a digital circuitelement forming the computing section 34 shown in FIG. 5.

FIG. 17 is a perspective view showing still another embodiment of theflow rate measuring unit according to the present invention, and FIGS.18A, 18B, and 18C are a plan view, front view, and side view of theunit, respectively. The present embodiment is different from the flowrate measuring unit of FIGS. 15 to 16C in that a flow rate measuringsection package 200 is attached to a unit substrate 220 in such a mannerthat the first to fourth terminals extend vertically with respect to theunit substrate 220.

FIG. 19 is a perspective view showing still another embodiment of theflow rate measuring unit according to the present invention, and FIGS.20A, 20B, and 20C are a plan view, front view, and side view of theunit, respectively. The present embodiment is different from the flowrate measuring unit of FIGS. 15 to 18C in that the package of theembodiment of FIGS. 13A to 14B is used as the flow rate measuringsection package 200.

FIG. 21 is a sectional view showing an embodiment of incorporation ofthe flow rate measuring section package according to the presentinvention into the flowmeter. In the present embodiment, a flow ratemeasuring section package similar to that of the embodiment of FIG. 2except shapes of wiring substrates 24. Opening end portion members 15 a,15 b are attached to opposite vertical ends of a fluid channel 14. Onthe other hand, the wiring substrates 24 is connected to a wiringsubstrate 25, and the wiring of the wiring substrate 25 is connected tothat inside a wiring housing section 25′. The wiring in the wiringhousing section 25′ is connected to the detection circuits 30, 32 shownin FIGS. 5 and 6.

FIG. 22 is a sectional view showing still another embodiment ofincorporation of the flow rate measuring unit according to the presentinvention into the flowmeter. In the present embodiment, the flow ratemeasuring unit of the embodiment of FIGS. 19 to 20C is used. The wiringof the unit substrate 220 is connected to that in the wiring housingsection 25′. The wiring in the wiring housing section 25′ is connectedto the computing section 34 shown in FIG. 5.

FIG. 23 is a diagram showing one embodiment of a piping leakageinspection apparatus or device according to the present invention. InFIG. 23, a tank 1, buried underground, for liquids (inflammable liquidssuch as gasoline, light oil, and kerosene) is connected to a piping 4for pumping out the liquid in the tank. In the piping, a check valve 6and a closed valve 8 intervene, the closed valve is opened during thepumping-out of the liquid, and the liquid is conveyed upwards via thecheck valve 6 by a drawing pump (not shown) disposed on the upper side(downstream side with respect to a liquid drawing direction).

The part of the piping 4 extending to the closed valve 8 from the checkvalve 6 is an inspection segment 7, and this part corresponds to apiping to be measured referred to in the present invention. The pipingto be measured 7 is buried underground, a branched part is disposedhalfway, and a connection end 5 for the connection to the leakageinspection apparatus is formed in the branched part.

On the other hand, a leakage inspection apparatus 50 of the presentembodiment has an internal piping system as shown. The internal pipingsystem includes a connection end 52 which communicates with the pipingto be measured 7, and a liquid discharge end 54. The inspectionapparatus 50 has a tank 56 for temporarily storing a pressurized liquid,connected to the internal piping system, and a pump 58 and a flowmeter60 disposed in order in a path extending to the connection end 52 fromthe tank 56 for temporarily storing the pressurized liquid in theinternal piping system. In the present embodiment, the pump 58 is a gearpump capable of feeding the liquid backwards. The internal piping systemhas a three-way electromagnetic valve, a check valve for protecting theflowmeter, a pressure sensor, and four electromagnetic valves (three ofthem are constantly closed [NC] and the other one is constantly opened[NO]) as the other constituting elements.

An operation of the leakage inspection apparatus of the presentembodiment will be described hereinafter together with a function of theinternal piping system with reference to FIGS. 24 to 27. The connectionend 5 on the side of the piping to be measured is connected to theconnection end 52 on the side of the inspection apparatus, so that theconnection end 52 communicates with the piping to be measured 7. It isto be noted that this connected state may be constantly maintained. Apipe is disposed between the liquid discharge end 54 of the inspectionapparatus and the underground tank 1.

FIG. 24 shows a liquid supply operation. Opened/closed states(OPEN/CLOSE) of four electromagnetic valves are set as shown, the pump58 is operated (backward liquid feeding operation) to thereby transferthe liquid to the tank 56 for temporarily storing the pressurized liquidfrom the piping to be measured 7 through the connection ends 5, 52without passing the liquid through the flowmeter 60 and three-wayelectromagnetic valve, and the liquid for inspecting the leakage isstored in the tank 56 for temporarily storing the pressurized liquid.This liquid transfer path is a first path.

FIG. 25 shows a pressurizing operation at the time of the leakageinspection. The opened/closed states of four electromagnetic valves areset as shown, and the pump 58 is operated (forward liquid feedingoperation) to thereby pressure-feed the liquid into the piping to bemeasured 7 from the tank 56 for temporarily storing the pressurizedliquid through the three-way electromagnetic valve, flowmeter 60, andconnection ends 52, 5. This liquid transfer path is a second path. Whenit is detected by the pressure sensor that the liquid pressure of thepart of the second path extending to the connection end 52 from the pump58 exceeds a set value (e.g., 20 kPa), the three-way electromagneticvalve positioned between the pump 58 and the flowmeter 60 is opened onan NC side, and a path (fourth path) for returning the liquid to thetank 56 for temporarily storing the pressurized liquid is formed. Thisoperation of the three-way electromagnetic valve is controlled based onan instruction from a CPU in the flowmeter 60 into which a signalindicating the value over the set pressure value is input from thepressure sensor.

In this inspection, after elapse of some time after starting the liquidpressure feeding by the pump 58, the signal indicating the value overthe set pressure value is input into the flowmeter from the pressuresensor, and thereafter the flow rate is measured by the flowmeter. Whenthe flow rate measured in this case exceeds a measurement error, it canbe judged that there is a leakage.

FIG. 26 shows a pressure release operation at the end of the inspection.The operation of the pump 58 is stopped, the opened/closed states offour electromagnetic valves are set as shown, the liquid pressure of atleast a part (on the downstream side from the check valve for protectingthe flowmeter) of the part of the second path extending to theconnection end 52 from the flowmeter 60 is released, and a part of theliquid is returned to the tank 56 for temporarily storing thepressurized liquid. This liquid transfer path is a fifth path.

FIG. 27 shows a liquid discharging operation after the end of theinspection. The opened/closed states of four electromagnetic valves areset as shown, the pump 58 is operated (forward liquid feeding operation)to thereby transfer the liquid to the liquid discharge end 54 from thetank 56 for temporarily storing the pressurized liquid through thethree-way electromagnetic valve, the flowmeter 60 and further anotherparallel path, and the liquid is returned into the underground burialtank 1. This liquid transfer path is a third path.

FIG. 28 is a diagram showing still another embodiment of the pipingleakage inspection apparatus according to the present invention. Thepresent embodiment is different from the embodiment of FIGS. 23 to 27 inthat a check valve for adjusting the pressure is used instead of thethree-way electromagnetic valve, and the three-way electromagnetic valveis used instead of one electromagnetic valve.

An operation of the leakage inspection apparatus of the presentembodiment will be described hereinafter together with the function ofthe internal piping system with reference to FIGS. 29 to 32.Additionally, here, respects different from those of the embodiment ofFIGS. 23 to 27 will be mainly described.

FIG. 29 shows a liquid supply operation. This operation is the same asthat described with reference to FIG. 24.

FIG. 30 shows a pressurizing operation at the time of the leakageinspection. This operation is substantially the same as that describedwith reference to FIG. 25. However, when the liquid pressure of the partof the second path extending to the connection end 52 from the pump 58exceeds the set value (e.g., 20 kPa) of a check valve for adjusting thepressure, the check valve for adjusting the pressure opens, and a path(fourth path) for returning the liquid into the tank 56 for temporarilystoring the pressurized liquid is formed.

FIG. 31 shows a pressure release operation at the end of the inspection.This operation is the same as that described with reference to FIG. 26.

FIG. 32 shows a liquid discharging operation after the end of theinspection. This operation is the same as that described with referenceto FIG. 27.

FIG. 33 is a diagram showing still another embodiment of the pipingleakage inspection apparatus according to the present invention. In thepresent embodiment, an electromagnetic pump incapable of feeding theliquid backwards is used as a pump 58′, and two electromagnetic valvesand three three-way electromagnetic valves are used in the internalpiping system.

An operation of the leakage inspection apparatus of the presentembodiment will be described hereinafter together with the function ofthe internal piping system with reference to FIGS. 34 to 37.Additionally, here, respects different from those of the embodiment ofFIGS. 23 to 27 will be mainly described.

FIG. 34 shows a liquid supply operation. A first path is formed throughthree three-way electromagnetic valves.

FIG. 35 shows a pressurizing operation at the time of the leakageinspection. A second path is formed through two three-wayelectromagnetic valves, and a fourth path is formed through onethree-way electromagnetic valve.

FIG. 36 shows a pressure release operation at the end of the inspection.A fifth path is formed through one three-way electromagnetic valve.

FIG. 37 shows a liquid discharging operation after the end of theinspection. A third path is formed through three three-wayelectromagnetic valves without passing through the flowmeter 60.

FIG. 38 is a diagram showing still another embodiment of the pipingleakage inspection apparatus according to the present invention. Thepresent embodiment is different from the embodiment of FIGS. 33 to 37 inthat a check valve for adjusting the pressure is added.

An operation of the leakage inspection apparatus of the presentembodiment will be described hereinafter together with the function ofthe internal piping system with reference to FIGS. 39 to 42.Additionally, here, respects different from those of the embodiment ofFIGS. 33 to 37 will be mainly described.

FIG. 39 shows a liquid supply operation. This operation is the same asthat described with reference to FIG. 34.

FIG. 40 shows a pressurizing operation at the time of the leakageinspection. A second path is the same as that of FIG. 35, but a fourthpath is formed through the check valve for adjusting the pressure.

FIG. 41 shows a pressure release operation at the end of the inspection.This operation is the same as that described with reference to FIG. 36.

FIG. 42 shows a liquid discharging operation after the end of theinspection. This operation is the same as that described with referenceto FIG. 37.

According to the leakage inspection apparatus of the above-describedembodiments of the present invention, the inspection apparatus itselftakes the liquid transferred in the piping to be measured, and performsthe pressurizing inspection using the liquid as the pressurized liquid.Therefore, an operation of extracting the liquid from the piping to bemeasured before the inspection, storing the liquid in another place, andreturning the liquid after the inspection, or an operation forintroducing a gas or a liquid for the inspection is not required, and aninspection operation is remarkably alleviated. Since the inspectionapparatus can be constantly connected to the connection end of thepiping to be measured, continuous inspection is easy, and early findingof the leakage is possible.

The flowmeter 60 is not especially limited, but a flowmeter capable ofmeasuring a micro amount is preferable. As the flowmeter capable ofcorrectly measuring a trace flow rate to a comparatively large flowrate, a flowmeter similar to that described with reference to FIGS. 1 to9 is illustrated.

FIG. 43 is a schematic sectional view showing one embodiment of aflowmeter 60. Since the flowmeter 60 is structurally similar to that ofFIG. 1, the description with reference to FIGS. 1 to 8 applies as such.

As shown in FIG. 43, a fine measuring tube 14 is disposed in acylindrical measuring tube 12, and a liquid (fluid) flows in the finemeasuring tube 14. In the present embodiment, the fine measuring tube 14is used as a fluid channel constituting an internal piping system. Whenleakage of the liquid from the piping to be measured 7 is generated, apredetermined pressurized state is realized at the time of leakageinspection, and thereafter the liquid passes in a direction of an arrowin the fine measuring tube 14.

The flow rate is measured in the same manner as described with referenceto FIGS. 1 to 8. Based on the flow rate measurement output from thecomputing section 34 as the result of the flow rate measurement, theleakage detection is performed in such a manner that it is judged thereis a leakage of the liquid in the piping to be measured in a case wherethe flow rate measurement exceeds a measurement error. This leakagedetection is preferably performed, for example, under conditions thatany liquid is not replenished into the tank or any liquid is not pumpedout of the tank at nighttime or the like. FIG. 44 shows one embodimentof a liquid leakage monitoring system utilizing the above-describedleakage detection of the piping, and further including the leakagedetection of the underground tank.

FIG. 44 shows a state in which a tank leakage detection device (tankleakage inspection device) 112 is inserted downwards into a in-tankliquid 2 from a measuring port of an underground tank. In the tankleakage detection device, the flowmeter is usable as described above. Onthe other hand, a piping leakage detection device (piping leakageinspection device) 50 is disposed which detects the leakage of theliquid from the piping to be measured 7.

The tank leakage detection device and piping leakage detection deviceare connected to individual monitoring apparatuses installed for eachtank in such a manner that signals can be transmitted/received byinternal communication means via cable or radio. The connection is madevia an I/O interface disposed in the piping leakage detection apparatusor the like, for example, as shown in FIG. 23. The individual monitoringdevice periodically (e.g., once a day) inquires the tank leakagedetection apparatus and the piping leakage detection apparatus,respectively, of results (presence of leakage, a degree [flow rate] ofthe leakage, etc.) of the detection (inspection). The leakage dataobtained from the leakage detection device is stored in the memory ofthe individual monitoring apparatus. The data stored in the memory isconstituted of a part indicating the tank leakage detection result, anda part indicating a piping leakage detection result. The descriptionwith reference to FIG. 9 applies to the apparatus of FIG. 44.

Industrial Applicability

As described above, according to the present invention, there areprovided a flow rate measuring method and a flowmeter, capable ofmeasuring a flow rate over a broad flow rate range from a trace flowrate region to a comparatively large flow rate region with satisfactoryprecision and sensitivity. According to the present invention, there areprovided a flow rate measuring method and a flowmeter, in which a dangerof fire by ignition is sufficiently reduced even in a case where fluidsare inflammable liquids such as fuel oils. Therefore, it is possible toeasily, correctly, and safely detect even a trace amount of fluid usingthe flow rate measuring method and flowmeter of the present embodiment.

Moreover, as described above, according to the present invention, thereare provided a flow rate measuring section package and a flow ratemeasuring unit preferably for use in a flowmeter which is capable ofmeasuring a flow rate over a broad flow rate range from a trace flowrate region to a comparatively large flow rate region with satisfactoryprecision and sensitivity and in which a danger of fire by ignition issufficiently reduced even in a case where fluids are inflammable liquidssuch as fuel oils and which is capable of easily, correctly, and safelydetecting even a trace amount of fluid leakage.

Furthermore, as described above, according to the present invention,there is provided a piping leakage inspection apparatus capable ofeasily and correctly detecting even a trace amount of leakage. Accordingto the present invention, there is provided a leakage inspectionapparatus capable of easily and efficiently performing leakageinspection utilizing a liquid which has been transferred into a pipingand which is left in the piping as a pressurized liquid.

1. A method of measuring a flow rate of a fluid in a fluid flow channel,comprising the steps of: obtaining a flow rate value obtained bymeasuring a flow rate of the fluid by indirectly-heatedconstant-temperature controlling flow rate measuring as a measurementwith respect to a high flow rate region larger than a boundary flow rateregion predetermined concerning a value of the flow rate; obtaining aflow rate value obtained by two-constant-point temperature differencedetecting flow rate measuring as a measurement with respect to a lowflow rate region smaller than the boundary flow rate region; obtaining aflow rate value obtained by the indirectly-heated constant-temperaturecontrolling flow rate measuring or a flow rate value obtained by thetwo-constant-point temperature difference detecting flow rate measuringas a measurement with respect to the boundary flow rate region; andusing a measuring section for the indirectly-heated constant-temperaturecontrolling flow rate measuring as a heat source which heats the fluidin the fluid flow channel in the two-constant-point temperaturedifference detecting flow rate measuring.
 2. The flow rate measuringmethod according to claim 1, wherein the boundary flow rate region isconstituted of one specific flow rate value only.
 3. The flow ratemeasuring method according to claim 1, further comprising the steps of:first measuring the flow rate of the fluid by the indirectly-heatedconstant-temperature controlling flow rate measuring; obtaining the flowrate value as the measurement, when the obtained flow rate value belongsto the high flow rate region or one of the high flow rate region and theboundary flow rate region; in another case, next measuring the flow rateof the fluid by the two-constant-point temperature difference detectingflow rate measuring; and obtaining the obtained flow rate value as themeasurement.
 4. The flow rate measuring method according to claim 1,further comprising the steps of: first measuring the flow rate of thefluid by the two-constant-point temperature difference detecting flowrate measuring; obtaining the flow rate value as the measurement, whenthe obtained flow rate value belongs to the low flow rate region or oneof the low flow rate region and the boundary flow rate region; inanother case, next measuring the flow rate of the fluid by theindirectly-heated constant-temperature controlling flow rate measuring;and obtaining the obtained flow rate value as the measurement.
 5. Aflowmeter which measures a flow rate of a fluid in a fluid flow channel,comprising: an indirectly-heated constant-temperature controlling flowrate measuring section and a two-constant-point temperature differencedetecting flow rate measuring section disposed facing the fluid flowchannel; and a computing section which obtains a measurement based on afirst flow rate corresponding output obtained using theindirectly-heated constant-temperature controlling flow rate measuringsection and a second flow rate corresponding output obtained using thetwo-constant-point temperature difference detecting flow rate measuringsection, wherein the indirectly-heated constant-temperature controllingflow rate measuring section has a heating element and a firsttemperature detecting element disposed adjacent to the heating element,the heating element is feedback-controlled based on a detectedtemperature of the first temperature detecting element, and the firstflow rate corresponding output is obtained based on a state of thefeedback control, the two-constant-point temperature differencedetecting flow rate measuring section has a second temperature detectingelement and a third temperature detecting element disposed on upstreamand downstream sides, respectively, of the indirectly-heatedconstant-temperature controlling flow rate measuring section withrespect to a fluid flowing direction in the fluid flow channel, and asecond flow rate corresponding output is obtained based on a differencebetween detected temperatures of the second and third temperaturedetecting elements, and the computing section outputs a flow rate valueobtained based on the first flow rate corresponding output as ameasurement with respect to a high flow rate region larger than aboundary flow rate region predetermined concerning the value of the flowrate, outputs a flow rate value obtained based on the second flow ratecorresponding output as a measurement with respect to a low flow rateregion smaller than the boundary flow rate region, and outputs a flowrate value obtained based on the first or second flow rate correspondingoutput as a measurement with respect to the boundary flow rate region.6. The flowmeter according to claim 5, wherein the boundary flow rateregion is constituted of one specific flow rate value only.
 7. Theflowmeter according to claim 5, wherein the computing section firstoutputs the flow rate value obtained based on the first flow ratecorresponding output as the measurement, when the first flow ratecorresponding output corresponds to the high flow rate region or one ofthe high flow rate region and the boundary flow rate region, and, inanother case, outputs the flow rate value obtained based on the secondflow rate corresponding output as the measurement.
 8. The flowmeteraccording to claim 5, wherein the computing section first outputs theflow rate value obtained based on the second flow rate correspondingoutput as the measurement, when the second flow rate correspondingoutput corresponds to the low flow rate region or one of the low flowrate region and the boundary flow rate region, and, in another case,outputs the flow rate value obtained based on the first flow ratecorresponding output as the measurement.
 9. The flowmeter according toclaim 5, wherein both the heating element and the first temperaturedetecting element have energizeable thin film shapes, and are stackedvia an electrically insulating thin film.
 10. The flowmeter according toclaim 5, wherein the first flow rate corresponding output is obtainedfrom a detection circuit including the heating element, the firsttemperature detecting element, and a temperature detecting element fortemperature compensation.
 11. A flow rate measuring section package formeasuring a flow rate of a fluid in a fluid flow channel, comprising: anindirectly-heated constant-temperature controlling flow rate measuringsection and a two-constant-point temperature difference detecting flowrate measuring section which are attached to the fluid flow channel, thetwo-constant-point temperature difference detecting flow rate measuringsection comprising an upstream-side temperature detecting section and adownstream-side temperature detecting section disposed on upstream anddownstream sides, respectively, of the indirectly-heatedconstant-temperature controlling flow rate measuring section withrespect to a fluid flowing direction in the fluid flow channel; whereinthe indirectly-heated constant-temperature controlling flow ratemeasuring section has a heating element and a first temperaturedetecting element disposed adjacent to the heating element, theupstream-side temperature detecting section has a second temperaturedetecting element, and the downstream-side temperature detecting sectionhas a third temperature detecting element, and the indirectly-heatedconstant-temperature controlling flow rate measuring section isconnected to a first wiring section for electric connection to theheating element and the first temperature detecting element, theupstream-side temperature detecting section is connected to a secondwiring section for electric connection to the second temperaturedetecting element, and the downstream-side temperature detecting sectionis connected to a third wiring section for electric connection to thethird temperature detecting element.
 12. The flow rate measuring sectionpackage according to claim 11, wherein one of the first, second, andthird wiring sections are all formed using flexible wiring substrates.13. The flow rate measuring section package according to claim 11,wherein the indirectly-heated constant-temperature controlling flow ratemeasuring section, the upstream-side temperature detecting section, thedownstream-side temperature detecting section, and a part of the fluidflow channel to which these sections are attached are housed in acasing.
 14. The flow rate measuring section package according to claim13, wherein first, second, and third terminals constituting the first,second, and third wiring sections, respectively, are extended from thecasing.
 15. The flow rate measuring section package according to claim14, wherein a temperature detecting section having a temperaturedetecting element for temperature compensation is accommodated in thecasing, the temperature detecting section is connected to a heattransfer member extending out of the casing, and a fourth terminalconstituting a fourth wiring for electric connection to the temperaturedetecting element for temperature compensation is extended from thecasing.
 16. The flow rate measuring section package according to claim11, wherein both the heating element and the first temperature detectingelement have energizeable thin film shapes, and are stacked via anelectrically insulating thin film.
 17. A flow rate measuring unit,comprising: the flow rate measuring section package according to claim1; a unit substrate for attaching the flow rate measuring sectionpackage; and a flow rate measuring circuit element attached to the unitsubstrate.
 18. The flow rate measuring unit according to claim 17,wherein the flow rate measuring circuit element includes an analogcircuit element.
 19. The flow rate measuring unit according to claim 18,wherein the analog circuit element feedback-controls the heating elementbased on a detected temperature of the first temperature detectingelement, obtains a first flow rate corresponding output based on a stateof the feedback control, and obtains a second flow rate correspondingoutput based on a difference between detected temperatures of the secondand third temperature detecting elements.
 20. The flow rate measuringunit according to claim 19, wherein the flow rate measuring circuitelement further includes a digital circuit element.
 21. The flow ratemeasuring unit according to claim 20, wherein the digital circuitelement comprises a computing section which obtains a flow ratemeasurement based on the first and second flow rate correspondingoutputs, and the computing section outputs a flow rate value obtainedbased on the first flow rate corresponding output as the measurementwith respect to a high flow rate region larger than a boundary flow rateregion predetermined concerning the value of the flow rate, outputs aflow rate value obtained based on the second flow rate correspondingoutput as the measurement with respect to a low flow rate region smallerthan the boundary flow rate region, and outputs a flow rate valueobtained based on the first or second flow rate corresponding output asthe measurement with respect to the boundary flow rate region.
 22. Theflow rate measuring unit according to claim 21, wherein the boundaryflow rate region is constituted of one specific flow rate value only.23. The flow rate measuring unit according to claim 21, wherein thecomputing section first outputs the flow rate value obtained based onthe first flow rate corresponding output as the measurement, when thefirst flow rate corresponding output corresponds to the high flow rateregion or one of the high flow rate region and the boundary flow rateregion, and, in another case, outputs the flow rate value obtained basedon the second flow rate corresponding output as the measurement.
 24. Theflow rate measuring unit according to claim 21, wherein the computingsection first outputs the flow rate value obtained based on the secondflow rate corresponding output as the measurement, when the second flowrate corresponding output corresponds to the low flow rate region or oneof the low flow rate region and the boundary flow rate region, and, inanother case, outputs the flow rate value obtained based on the firstflow rate corresponding output as the measurement.
 25. A piping leakageinspection apparatus which inspects a leakage of a liquid from a pipingto be measured, comprising: an internal piping system comprising aconnection end for communication with the piping to be measured, and aliquid discharge end; a tank for temporarily storing a pressurizedliquid, which is connected to the internal piping system; and a pump anda flowmeter disposed in order in a path extending to the connection endfrom the tank for temporarily storing the pressurized liquid in theinternal piping system, wherein the internal piping system is capable offorming a first path which transfers the liquid into the tank fortemporarily storing the pressurized liquid from the piping to bemeasured through the connection end by the pump without passing theliquid through the flowmeter, a second path for pressure-feeding theliquid into the piping to be measured from the tank for temporarilystoring the pressurized liquid through the flowmeter and the connectionend by the pump, and a third path for transferring the liquid into theliquid discharge end from the tank for temporarily storing thepressurized liquid by the pump, and the leakage of the liquid from thepiping to be measured is inspected based on a liquid flow rate detectedby the flowmeter at a time when a liquid pressure of a part of thesecond path extending to the connection end from the pump is raised bythe liquid pressure-feeding by the pump in a state in which theconnection end is connected to the piping to be measured.
 26. The pipingleakage inspection apparatus according to claim 25, wherein the internalpiping system is capable of forming a fourth path which returns theliquid into the tank for temporarily storing the pressurized liquid froma part between the pump and the flowmeter in a case where the liquidpressure of the part extending to the connection end from the pumpexceeds a set value in the second path.
 27. The piping leakageinspection apparatus according to claim 25, wherein the internal pipingsystem is further capable of forming a fifth path for releasing theliquid pressure of at least a part of the part extending to theconnection end from the flowmeter in the second path.
 28. The pipingleakage inspection apparatus according to claim 25, wherein theflowmeter comprises: an indirectly-heated constant-temperaturecontrolling flow rate measuring section and a two-constant-pointtemperature difference detecting flow rate measuring section disposedfacing a fluid flow channel constituting the internal piping system; anda computing section which obtains a measurement based on a first flowrate corresponding output obtained using the indirectly-heatedconstant-temperature controlling flow rate measuring section and asecond flow rate corresponding output obtained using thetwo-constant-point temperature difference detecting flow rate measuringsection, the indirectly-heated constant-temperature controlling flowrate measuring section has a heating element and a first temperaturedetecting element disposed adjacent to the heating element, the heatingelement is feedback-controlled based on a detected temperature of thefirst temperature detecting element, and the first flow ratecorresponding output is obtained based on a state of the feedbackcontrol, the two-constant-point temperature difference detecting flowrate measuring section has a second temperature detecting element and athird temperature detecting element disposed on upstream and downstreamsides, respectively, of the indirectly-heated constant-temperature.controlling flow rate measuring section with respect to a fluid flowingdirection in the fluid flow channel, and the second flow ratecorresponding output is obtained based on a difference between detectedtemperatures of the second and third temperature detecting elements, andthe computing section outputs a flow rate value obtained based on thefirst flow rate corresponding output as a measurement with respect to ahigh flow rate region larger than a boundary flow rate regionpredetermined concerning the value of the flow rate, outputs a flow ratevalue obtained based on the second flow rate corresponding output as ameasurement with respect to a low flow rate region smaller than theboundary flow rate region, and outputs a flow rate value obtained basedon the first or second flow rate corresponding output as a measurementwith respect to the boundary flow rate region.
 29. The piping leakageinspection apparatus according to claim 28, wherein the boundary flowrate region is constituted of one specific flow rate value only.
 30. Thepiping leakage inspection apparatus according to claim 28, wherein thecomputing section first outputs the flow rate value obtained based onthe first flow rate corresponding output as the measurement, when thefirst flow rate corresponding output corresponds to the high flow rateregion or one of the high flow rate region and the boundary flow rateregion, and, in another case, outputs the flow rate value obtained basedon the second flow rate corresponding output as the measurement.
 31. Thepiping leakage inspection apparatus according to claim 28, wherein thecomputing section first outputs the flow rate value obtained based onthe second flow rate corresponding output as the measurement, when thesecond flow rate corresponding output corresponds to the low flow rateregion or one of the low flow rate region and the boundary flow rateregion, and, in another case, outputs the flow rate value obtained basedon the first flow rate corresponding output as the measurement.
 32. Thepiping leakage inspection apparatus according to claim 28, wherein boththe heating element and the first temperature detecting element haveenergizeable thin film shapes, and are stacked via an electricallyinsulating thin film.
 33. The piping leakage inspection apparatusaccording to claim 28, wherein the first flow rate corresponding outputis obtained from a detection circuit including the heating element, thefirst temperature detecting element, and a temperature detecting elementfor temperature compensation.